The Corcoran Gallery of Art’s dramatic plan to dissolve and reorganize with new caretakers received a major boost with the endorsement late Wednesday of District Attorney General Irvin B. Nathan, while opponents issued their most elaborate critique and proposed an alternative to the breakup of Washington’s oldest private art museum and college.

The hundreds of pages of dueling court briefs, plus the release of passionate written comments from 53 members of the public, set the battle lines of argument for a public hearing scheduled for 2:30 p.m. Friday before Judge Robert Okun in D.C. Superior Court. Lawyers said it is unclear whether Okun will decide the matter Friday, issue a ruling in coming days or order more proceedings.

The legal team from Nathan’s office — which regulates charities such as the Corcoran and represents the District in this matter — said in its brief that the plan to give the art college to George Washington University and a large fraction of the Corcoran’s 17,000 artworks to the National Gallery of Art is the best solution to a bad situation.

“The District supports [the reorganization] because [it] will allow the Corcoran’s assets to continue to be used in D.C. consistently with the charitable purposes to which they have been dedicated,” the city lawyers said in the filing.

Nathan’s office accepted the Corcoran’s contention that, after years of budget deficits and failed fundraising, the institution can no longer function as founder William W. Corcoran imagined in 1869. The city lawyers agreed that the deal with GWU and the National Gallery is the next best means of carrying on the original mission.

Before the plan can proceed, Okun must grant permission for the Corcoran to revise William Corcoran’s original deed of trust that set up the gallery. The Corcoran College of Art & Design opened in 1890, shortly after Corcoran’s death.

However, opponents — including the advocacy group Save the Corcoran and a dozen students, donors and former faculty and staff members — countered that the Corcoran has failed to provide sufficient evidence to prove its case.

For example, the Corcoran submitted to the court just a quarter-page of summary financial information and an incomplete set of documents related to the deal with GWU and the National Gallery, an attorney for the opponents argued in his brief.

“The [Corcoran] trustees have not met their burden of proving that the Corcoran trust has become impracticable,” the attorney wrote. “Nor have they established that the proposed dissolution is ‘as close as possible ’ to the original terms and purposes of that trust, and that the Corcoran cannot survive — and thrive — as an independent institution.”

Instead of committing to contribute $48 million to the arrangement with GWU and the National Gallery, the Corcoran should use some of that money to stay independent and build a future, the opponents say. As a last resort, the Corcoran should also consider selling art to raise funds.

The Corcoran and the attorney general point out that selling art for operations could cause the Corcoran to lose its museum accreditation.

Yet on that point as well, the opponents argue, the Corcoran has not proved that a loss of accreditation by the American Alliance of Museums would be more devastating to the Corcoran legacy than the proposed breakup.

“Is AAM accreditation so vital that you need to bring the whole house down — when you can [get] AAM accreditation back?” Andrew Tulumello, the opponents’ attorney, said in an e-mail. “If W.W. Corcoran were here today, would he say: Take everything I built, everything I collected, the building created under my trust, vaporize the school — and give it all away because the AAM won’t give me the seal of approval?”

Even former Corcoran director Paul Greenhalgh suggested selling art in a five-page memo — not previously disclosed — that he wrote to the Corcoran board early last year, which Tulumello attached as an exhibit to his brief.

“The good news is that surprisingly few works need to be deaccessioned in the current market to raise at least $100M,” Greenhalgh wrote.

The consequences of losing accreditation include loss of reputation and possibly being unable to borrow art from other museums.

“The District does not dismiss the potential consequences of the Corcoran’s loss of accreditation so easily,” the city lawyers argued. “Save the Corcoran’s proposal is a short-term fix that will not alleviate the longer-term problems that the Corcoran faces.”

The attorney general’s office also dismissed the critics’ attempt to “look back” and charge that Corcoran leaders’ own mismanagement deepened the crisis and that their removal could make a difference.

“Whether or not these assertions have merit . . . the District must, and the court should, look at the situation and the consequences as they exist now,” the city lawyers said.

The opponents are calling on Okun to order a second hearing on what they call “unanswered questions,” while the Corcoran and the attorney general maintain that further delay could imperil the coming school year and — in the worst case — force the closing of both the gallery and the school.

Public comments submitted to the court expressing concern outnumbered supporters 39 to 14. Former Corcoran director Michael Botwinick said there wasn’t enough time for careful consideration. Former director Roy Slade asked that William Corcoran’s name be preserved and for the masterworks of American art to be kept together.

Former chief curator Jane Livingston described her “relief” and “gratitude” that the National Gallery and GWU would step in. Student Lucien Liz-Lepiorz said GWU has the resources to provide a good education.

Meanwhile, the Howard University Gallery of Art is looking on the bright side. Director Gwendolyn Everett wrote to say Howard would be happy to take the Corcoran’s Evans-Tibbs Collection of African American Art, if the National Gallery doesn’t want it.